1. science
2. geography
3. topography

INTERCEPTION OF RAINFALL BY A REDWOOD CANOPY IN THE NORTH COAST OF CALIFORNIA by Michael T. Rains A Thesis Presented to The Faculty of Humboldt State College In Partial Fulfillment of the Requirements for the Degree Master of Science January, 1971 INTERCEPTION OF RAINFALL BY A REDWOOD CANOPY IN THE NORTH COAST OF CALIFORNIA by Michael T. Rains Approved by the Mater's Thesis Committee Approved for the Graduate Study Committee INTERCEPTION OF RAINFALL BY A REDWOOD CANOPY IN THE NORTH COAST OF CALIFORNIA (Michael T. Rains, Humboldt State College, Arcata, California) Rainfall interception losses and net throughfall amounts ABSTRACT:R
were compared with gross rainfall in a redwood (Sequoia sempervirens (D. Don) Endl.) stand in the fall season of 1970. A total of 15 storms were studied. Since stemflow was shown to be insignificant, intercep­
tion loss was the difference between gross rainfall and net through-
fall. The study area was the NW1/4, SE1/4, Sec. 28, T5N, R1E in Fresh­
water, California. Five study plots were used, each containing six sample trees. Trees of dominant, co-dominant, and intermediate crown classes were used. Basic number 10 cans were used as "catch cans" and placed at intervals of 2, 4, and 6 feet from the tree bole. Recording raingages were used to measure gross rainfall. Net throughfall ranged from 60.4% to 82.8% of gross rainfall. Net throughfall is a linear function of gross rainfall and is closely correlated to storm intensity, rainfall amount, and crown length. There also seems to be a relationship between net throughfall and basal area per acre but since I only sampled certain clusters of trees as a part of the entire stand and thus do not have acceptable "samples" of stand stocking, this can only be stated as a possible relation. Average interception losses were found to range from 17.2% to 36.9% of gross rainfall and crown length, and is also closely related to storm intensity, storm frequency, rainfall amount and possibly to basal area per acre. iii A statistical analysis of the data indicated that the number of sample cans were adequate for the investigation. iv ACKNOWLEDGMENTS The author wishes to express a special thanks to his major Professor, Dr. F. Dean Freeland for his long and continued help with this study. I would also like to thank E. Nelson Dean, Cheri Hollinger and Wendy Murray for their help with the field work. I would like to thank the other members of my Committee, Dr. Dale Thornburgh, Mr. Louis Powell, Dr. D. Hedrick and Dr. James Koplin, for their guidance and review of this manuscript. Finally, I wish to express gratitude to my parents for their continued encouragement with this study. TABLE OF CONTENTS Page ABSTRACT...INTERCEPTION OF RAINFALL BY A REDWOOD CANOPY IN THE NORTH COAST
ACKNOWLEDGMENTS
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iii
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LIST OF TABLESR
LIST OF FIGURES
vii R
viii I SCOPE AND PURPOSER
1
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3
II A THEORY OF INTERCEPTION
III TERMINOLOGY
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7
IV A LITERATURE REVIEW OF NET THROUGHFALL, INTERCEPTION, AND STEMFLOW
V STUDY AREA
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8
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15 VI STUDY METHODS
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20 VII RESULTS AND DISCUSSIONS
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35 VIII SUMMARY AND CONCLUSIONS
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63 IX LITERATURE CITED
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67 X APPENDIX
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70 vi
LIST OF TABLES Page Table 1. Summary description of study plots R
19 2. Tree number and "throughfall can" distribution at distances from the tree bole R
20 R
3. Rainfall Summary - Gross Rainfall
4. Rainfall Summary - Net Throughfall (inches)
5. Rainfall Summary - Net Throughfall (percent) R
40 6. Rainfall Summary - Interception (inches) R
49 7. Rainfall Summary - Interception (percent)
8. Net Throughfall Summary - Net throughfall percentages with basal area per acre for each study plot R
9. 38 39 R
R
50 51 Interception Summary - Interception percentages 61 with basal area per acre for each study plot R
vi i
LIST OF FIGURES Page FigureR
1. Aerial view of study area. N1414, 5E4, Sec. 28, T5N, R1E, H.M. (Humboldt County Photo HC-66, 18-29, flown by H. J. Chickering Jr. Corp., Eugene, Oregon, 1966)
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17 2. Map of NW1/4, 5E4, T5N, R1E, Sec. 28 showing plot location and recording raingage distribution
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3. Relative canopy density for plot #1 R 25 4. #10 can location at 2 and 6 feet from tree bole on plot #4
26 R
5. Relative canopy density for plot #2 R 27 28 . .R
6. Recording raingage set-up for plots #2 and #3R
7. Relative canopy density on plot #4
29 R
8. #10 can set-up at intervals of 2, 4, and 6 feet from tree bole on plot #3
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30 31 9. Recording raingage set-up for plot #1 R
32 10. #10 can set-up and locale for plot #5 R
11. #10 can set-up on plot #2
33 R
12. #10 can set-up and area of plot #2
34
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13. Linear regression comparing net throughfall with gross rainfall at distances of 2, 4, and 6 feet R
41 from tree bole 14. Linear regression comparing average net throughfall with gross rainfall at all R
43 distances within the tree canopy 15. Net throughfall in relation to gross rainfall at distances
of 2, 4, and 6 feet from the
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tree bole vi i i
44
FigureR
Page 16. Net throughfall (percent of gross rainfall) in relation to gross rainfall (inches)
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45 17. Average net throughfall per plot in relation to tree basal area per acre
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46 18. Linear regression comparing interception with gross rainfall at distances of 2, 4,
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and 6 feet from tree bole 53 19. Linear regression comparing average interception with gross rainfall at all distances within the tree canopy
20. Linear regression comparing average interception with average crown length per plot at 2 and 6 feet from the tree bole R
54 R
56 21. Interception (percent) in relation to gross rainfall
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58 22. Average interception per plot in relation to tree basal area per acre
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59 23. Interception in relation to gross rainfall at distances of 2, 4, and 6 feet from tree bole
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60 24. Bar graph comparing total net throughfall and interception for entire fifteen storms studied . . . .R
62 ix
I SCOPE AND PURPOSE In vegetated regions, plant surfaces are one of the first obstructions precipitation encounters in its journey through the hydro­
logic cycle. The term interception is applied to this phenomenon and includes all processes that affect the catchment, storage and dis­
position of precipitation on plant and litter surfaces. As civilization advances, the industrial, domestic and agri­
cultural needs for water increase and the uses of water become more complex in many parts of the world. Therefore, scientific management of water has become very important. While the beneficial effects of forest in conserving the soil, moderating the local climate, and similar functions are well recognized, the hydrological benefits of the forest are often disputed. Interception of rain by the forest canopy is a factor of sufficient magnitude to require its measurement in any complete study of the hydrology of forested watersheds. Scientific investigations concerning rainfall interception have been conducted in various parts of the world for over a century (Hoppe, 1896) and has probably received more atten­
tion than any other component of the forest water balance. In most of these studies, it has been shown that the amount of precipitation reaching the ground varies with the character of the forest, character of the precipitation and wind velocity, among other factors. Because of these variables, it is evident that interception records made in one forest type and age class cannot be of general application. Summaries of forest interception studies in the United States have shown that losses due to interception range from 10 to 35 percent of 2
annual precipitation (Zinke, 1967; Kittredge, 1948). With losses as great as this, it is apparent that rainfall interception is a vital factor in proper watershed management. Field studies by Leyton et al. (1967), Patric (1966), Rutter (1963), and Helvey (1967) indicate that interceptional losses have a significant impact on water yields for a given watershed. Leonard (1961) and Rothacher (1963) concluded: "A forest canopy significantly influences the hydrology of an area by reducing the amount of precipitation that reaches the ground." In the afforestation programs of many countries, many new species are frequently introduced from differing climatic regions. These young forests are frequently located in water catchment areas and in dry regions where the shortage of water may limit the tree growth. More work in this field under various situations seems essential to have a full understanding of the interception process and what effect species may have on the water regime. The objectives of this investigation are: 1) to determine the relationship of interception losses with gross rainfall, 2) to determine the relationship of net throughfall with gross rainfall, 3) to study selected stand conditions that affect interception and net throughfall, and 4) to study quantitatively the amounts of these interception losses and throughfall with respect to gross rainfall. II THEORY OF INTERCEPTION A leaf is able to absorb little if any water from its surface. The storage capacity of a leaf may then be considered to be the amount of water a leaf is able to retain on its surface. The amount of water held on the surface will be a function of: leaf size, leaf surface configuration and composition, viscosity of the water, and external pressure on the liquid, as well as amount of precipitation. These combined factors produce a surface tension between the leaf surface and the water on the surface. A closer examination of this system reveals that when rains begin, drops striking the leaves are largely retained on the leaf surface. A portion of the drops may spatter from the leaf surface due to the high impact velocity of the large drops formed during the descent through the lower atmosphere. The moisture retained on the leaf slowly spreads out from the point of drop impact into a thin film. This continues until the storage capacity of the leaf is filled or the surface tension forces are in balance with the gravitational forces. Thereafter drops striking the leaf form miniature pools and rivulets channeling the moisture to the tips or lower edges of the leaves where they form into drops. Drop size gradually increases until forces due to gravity overcome the forces due to adhesion and cohesion. When the ratio of gravitational forces to surface tension forces exceeds unity the drop will separate from the edge of the leaf, falling downward to strike a lower leaf or pass through the interleaf spaces to the ground. Large drops of moisture have an increasing velocity with distance of drop until a terminal velocity is reached. Surface tension forces on 4
the leaves in the lower portion of the canopy may be overcome because of the impact velocity of the large drops falling from the edge of the upper leaves. Total canopy storage will be a function of leaf area, surface tension ratio, storm intensity and storm size. Canopy storage will be dependent on storm size to the point of maximum storage. It is important to note that after the storage has reached a maximum, storm size becomes unimportant in storage considerations. However, storage may or may not equal gross precipitation, up to this time, due to drops falling through the canopy. Evaporation losses taking place within the canopy during the storm period are an important part of the interception process. The magnitude of evaporation during storm periods is indeed significant. Horton (1919) speaks of evaporation rates as high as 0.02 to 0.09 inches per hour for a given storm. The Second Law of Thermodynamics states that "all systems tend toward equilibrium." It follows from the Second Law that in a liquid-
vapor system a change of state from the liquid to the vapor phase (evaporation) will be a continuing process until a state of equilibrium is reached. According to Munn (1961) the rate of evaporation will depend on (1) availability of water at the surface, and (2) rate of diffusion of water vapor away from the surface. Applying the criteria to the intercepted precipitation in the canopy, the rate of evaporation will increase until storage capacity of the leaf is satisfied. Assuming ample precipitation in a storm, the amount of water retained by the leaf or its storage will be dependent on leaf area and surface tension forces. The surface tension is in part a function of 5
leaf surface configuration, liquid viscosity and mechanical activity. Leaf surface configuration will vary by type and condition of leaves within the canopy. This may change with season of the year, insect activity and growth factors. Leaves may become smooth during the latter part of the growing season. Insects may deposit egg masses or leave a fine network of lacy intersurfaces, increasing storage capacity. Surface tension increases with an increase in viscosity. Viscosity increases with a decrease in temperature. A large, heavily veined, rough-textured leaf in still, cool air should have a maximum storage capacity. This aspect of the interception processes may be a possible explanation for the relatively high interception values noted by Beall (1934) and others during the early spring and late autumn when deciduous vegetation is in a leafless condition. The lower temperatures with consequent higher viscosity and surface tension forces could result in a higher storage capacity of the bark and twigs during the leafless period. Another aspect of storage capacity is the orientation of the leaf in the canopy. A leaf at right angles to the gravitational force will have a larger storage capacity than one parallel to the gravitational force. The distance between leaves in the vertical plane of the canopy may also play a part in the retention of moisture. Laws (1941) noted that when the leaves reach the point of maximum storage, rate of vapor diffusion away from the saturated leaf may be the limiting factor. Rate of diffusion is a function of the temperature and vapor pressure differential of the system. Most investigators who have concerned themselves with the problem of evaporation of intercepted rainfall have considered evaporation rate to be constant after storage capacity is filled (Horton, 1919; Linsley et al., 1949). 6 Still another aspect of the evaporation processes as they con­
tribute to interception may be found in the Law of Conservation of Energy. Phase transfer from liquid to vapor has a high energy require­
ment. During periods of frontal rainfall, temperature conditions within the forest are adiabatic and the radiation balance near zero. These factors all tend to decrease evaporation rate to an extremely low level in prolonged periods of precipitation. Evaporation rate then will be an inverse function of storm intensity assuming there is no wind activity. This case may be particularly important in periods of prolonged low intensity precipitation. TERMINOLOGY Terminology in this thesis is essentially that of Hamilton and Rowe (1949) and is as follows: Interception is the process by which rainfall is caught by the vegetative canopy, and redistributed as throughfall, stemflow, and evaporation from the vegetation. Throughfall is that portion of the rainfall which reaches the ground directly through the vegetative canopy, through intershrub species in the canopy, and as drip from the leaves, twigs, and stems. Stemflow is that portion of the rainfall which, having been intercepted by the canopy, reaches the ground by running down the stems. Interception loss is that portion of the rainfall which is retained by the aerial portion of the vegetation. Gross rainfall is the total amount of rainfall measured in the open or above the vegetative canopy and directly applicable to a particular area. Net rainfall is the quantity which actually reaches the ground. It is the sum of the throughfall and stemflow. III REVIEW OF LITERATURE Rainfall Interception Many experiments have been conducted in various parts of the world to determine what portion of the precipitation falling on the tree crowns eventually reaches the ground. Most of this work has been started in three studies. Horton (1919) summarized much of the existing data on interception while presenting results of his own research. Wicht (1941) brought the subject further up to date with his historical review of the work of many investigators. Kittredge (1948) gave an excellent resume of interception research in his book Forest Influences, and summarized a number of later studies. Early work was started in Central Europe and, according to Hoppe (1896) began with Krutzsch in 1864. Hoppe, working with the Austrian Forest Experiment Station, set up the first complete study on rainfall interception during the summers of 1894 and 1895. He found that the amount of catch was directly related both to the distance of the gauges from the stems and the intensity of the rain. Interception percent in a 50-year Norway spruce (Picea excelsa Link) stand was found to decrease progressively from positions near the stems outward into the openings from 45 percent to 24 percent, and from 34 percent to 17 percent in a 65­
year stand of Scotch pine (Pinus sylvestris L.). In a pine-hardwood stand in the Ouachita Mountains of Arkansas, throughfall was strongly correlated with gross rainfall. Total inter­
ception averaged 15.1 percent of average annual gross rainfall and stemflow 2.4 percent. Thus, average annual interception loss was 12.7 percent (Lawson, 1967). In a similar study, Semago and Nash (1962) 9
reported an average of 83.2 percent throughfall in summer and fall storms in a hardwood stand in Missouri. Helvey and Patric (1965) reported that throughfall in mature stands of hardwoods in the eastern United States averaged between 85-90 percent of annual precipitation. Boggess (1956) reported interception ranging from 8-11 percent of precipitation in young shortleaf pine (Pinus echinata Mill.) stands in Illinois. In a study done in Ontario with a 40-year old stand of red and white pine (Pinus resinosa Ait., Pinus strobus L.) by Beall (1934) for 16 inches of rain from May to October, 57 percent was intercepted at one foot from the bole, 27 percent under average crowns, and 16 percent in a small opening. Rogerson and Byrnes (1968) determined that throughfall averaged 80 percent of gross summer precipitation both under a red pine (Pinus resinosa Ait.) plantation and natural hardwood stands in Central Pennsylvania. In a mature stand of Jeffrey pine on the San Bernardino National Forest, Munns (1917) found that the percentage of interception was higher near the base of the tree than under the edge of the crown. Under isolated trees in Connecticut, Lunt (1934) found the percentage of interception generally decreased radially outward from the stems. Under the edge of a white pine crown, a negative interception of -11.2 percent was attributed to the dripping from the foliage and the ends of the branches. In a study by De Walle and Paulsell (1969) on the 12.48­
acre Gum Springs Watershed at the University of Missouri School Forest, it was found that 83 percent of precipitation from all storms reached the forest floor as throughfall. Two years of measurements on plots located at 8,200 feet on the Wasatch Front in central Utah, indicated that during 20 rainstorms up to 0.58 inch in size, and averaging 0.24 inch per storm, interception by aspen herbaceous cover averaged 35 percent (Monninger, 1950). 10 In a six-year study to determine interception loss in a fully stocked 65-75 year old second-growth ponderosa pine (Pinus ponderosa Laws.) stand situated near Bass Lake, California, it was found that 84 percent reached the forest floor as throughfall and 4 percent as stemflow. The average annual precipitation was 47 inches. (Rowe and Hendrix, 1951). Low atmospheric humidity and high evaporating power of the air tend to increase interception. For example, in a stand of ponderosa pine (Pinus ponderosa Laws.) at an elevation of 7,250 feet in Arizona, Pearson (1913) found interception averaging 40 percent. The surprisingly high figure of 40 percent may be ascribed to the high evaporating power of the air in that region. Rothacher (1963) noted that in mature Douglas fir (Pseudotsuga menziesii Mirb.), throughfall was related to crown density. Skau (1964) reported that interception by Utah juniper (Juniperus osteosperma (Torr.) Little) varied directly with crown density. Kittredge et al. (1941) summarizing the results of a seven-year study of interception in a 28-year old Monterey pine (Pinus radiata D. Don) plantation at Berkeley, California, concluded that interception varies under different parts of the crowns and in the openings. They found that interception percent was highest near the stem and decreased with increased distance from the bole. They also found highest average interception percent on the leeward side of the tree, while the lowest average inter­
ception (13%) was recorded beneath the crown periphery. An increase in wind velocity gave a higher interception but as the distance from the stem decreased interception was less. Studies by Beall (1934), Hoppe (1896) and Reynolds and Leyton (1963) showed that throughfall under forest trees varied directly with distance from tree trunks. Horton (1919) concluded: 11 "1. Rainfall interception represents a loss of precipi­
tation which would otherwise be available to the soil. 2. The loss takes place through evaporative processes, but may for convenience be subdivided into (a) inter­
ception storage, and (b) evaporation during the rain. 3. The amount of interception loss is primarily a function of the storage capacity of the plant surface, the duration of precipitation, and the evaporation rate during precipitation. 4. Since there is generally a fairly close correlation between shower duration and amount of precipitation, estimates of interception loss, can for practical purposes, be expressed in terms of precipitation amount per shower..." Subsequently Zon (1927), Kittredge et al. (1941), Ovington (1956) and Gilbert (1953) have subscribed to the same conclusions. Kittredge, in Forest Influences, proposed several new theories concerning the interception process. He modified somewhat the symbols used in Horton's original equations for interception and he restated the equations. The basic equation, as given by Kittredge, is I = S + KET . . where I is the depth of water intercepted, S is the depth of interception storage, both I and S on the projectional area of the crowns, K the ratio of the evaporation leaf surface to the projectional area, and E the evaporation rate in inches - depth per hour during the rain, and T the duration of the storm in hours. Both Horton and Kittredge assumed that percent interception decreases with increased duration of rain period if intensity remains constant, and also decreases with increase in rain intensity if duration of rain is constant. Some studies have been conducted on the effects of hardwood stands on interception loss. Zon (1927) concluded that a broad-leaf 12 forest intercepts about 13 percent of the rainfall annually. Mitchell (1930) reported that a hardwood-hemlock stand in northern Wisconsin withheld 25 percent of the rainfall during the leaf period and 16 percent of the rainfall during the leafless period, an average of 18 percent annually. Trimble and Weitzman (1954) found that Appalachian hardwood canopies intercept approximately 25 percent of the annual gross rainfall. Kittredge (1948) concluded that: "1. Interception losses vary with crown density: well stocked stands intercept more precipitation than those understocked; stands at ages between the closing of the canopy and culmination of the current annual increment intercept more than those younger or older. 2. Interception losses vary with species and forest types because of differences in thickness and density of foliage and crowns. Hence, tolerant species intercept more than intolerant, climax more than preclimax, and mesophytic more than xerophytic. 3. Interception varies within a stand, being greatest near the stems and least under the edges of the crowns and in the openings." Stemflow The amount of water reaching the forest floor by stemflow was assumed by many earlier workers to be insignificant, and consequently was not measured. This assumption is probably valid for relatively mature deciduous stands dominated by rough-barked trees and coniferous stands of closed canopy. Several interception studies conducted in American beech (Fagus grandifolia Ehrh.) stands revealed that as much as 10 percent of the summer rain falling on the canopy may reach the soil surface by stem-
flow. (Gilbert, 1953). According to Voigt (1960) stemflow is not at 13 all insignificant. Stemflow from a 10-inch beech for a 1.00 inch storm was equivalent to about 30 gallons of water. Leonard (1961) stated that stemflow was measured from 20 storms ranging in size from 0.07 inch to 1.47 inches. During the period of measurements, 5 percent of the rainfall measured in the open reached the forest floor by running down the stem. In another study in the Ouachita Mountains of Arkansas with a pine-hardwood stand, stemflow averaged 2.4 percent of gross annual precipitation which was 42.45 inches (Lawson, 1967). Helvey (1967) states stemflow varies inversely with stand age. Measured stemflow was 8.8, 4.3, and 2.3 percent of gross rainfall in 10-, 35-, and 60-year old stands respectively in the Southern Appalachians of North Carolina. Stemflow in certain brush species in California increased approxi­
mately as the square of basal diameter of stem, according to Rowe (1948). This was associated with the deliquescent habit of these species as a result of which several stems, each carrying some volume of stemflow, converged toward the base and thus both number of stems and amount of stemflow were correlated with diameter. Also, the larger shrubs were generally taller and more exposed and offered a larger intercepting surface to the rain-bearing winds. The volume of stemflow increased with increase in stem diameter and the percentage stemflow decreased with increase in crown area, according to Hoppe's (1896) records from five beech trees in Austria. For Cryptomeria in Japan, Hirata (1929) reports stemflow beginning with precipitation of 0.2 inch and reaching a maximum of 11 percent in rains of 4.6 inch per 24 hours. Shortleaf pine stands, 25 years old, in North 14 Carolina yielded 1 to 5 percent of the precipitation as stemflow (Sims, 1932). Mature lodgepole pine (Pinus contorta Dougl.) in Colorado yielded less than 0.1 of one percent of the precipitation as stemflow. A 32-year old stand yielded 1.5 percent while a near-by stand of aspen (Populus tremuloides Michx.) of the same age yielded only 1.1 percent (Dunford and Niederhof, 1944). This low stemflow for the smooth-barked aspen is an exception to the evidence that stemflow is large from smooth-
barked species. The stemflow for 86-year old beech in Austria (Hoppe, 1896) began at less than 0.1 in precipitation and reached as much as 21 percent of the precipitation in rains of 1 inch. The average for the beech stand for all the rains was 15.4 percent. Kittredge et al. (1941) concluded that stemflow usually commences to add moisture to the ground when the precipitation was in excess of 0.2 to 0.25 inch. Stemflow, according to him, was not related to crown-
length density, tree height, basal area, or crown area, but it tended to increase with excess or deficit of height of tree as compared with adjacent trees. No reports nor literature references on studies in the redwood region or redwood species concerning rainfall interception and stemflow were found. IV STUDY AREA The area selected for this study was Humboldt State College's School Forest in Freshwater. The forest is located in Sections 28 and 33, Township 5 North, Range 1 East, Humboldt Meridian. The area was selected because of its convenience and the availability of pure red­
wood stands. The area where the individual plots are located is in the NW1/4, SE1/4, of Section 28. Figure #1, page 17, shows this portion in relation to the surrounding locale. Figure #2, page 18, is a map of this NW1/4, 5E4, of Section 28. This figure shows the individual study plots and the recording raingage distribution. The study plots ranged in elevation from 120 to 160 feet above sea level. All are near or on the bottom of a drainage area. Table #1, page 19, gives a summary description of the five study plots. Freshwater Forest is located in a humid, microthermal region characterized by low summer rainfall. It has an annual precipitation of about 38.4 inches, according to the Eureka Weather Station, Eureka, California. All of this precipitation falls in the form of rain. The temperature ranges from a low of 22° F to a high of 85° F with an average of 52.3° F. However, the average variance in temperature is from 47.4° F in January to 56.7° F in August. These temperatures were recorded at the Eureka Weather Station. This forest has an elevational range from 60 to 500 feet above sea level. It has a vegetative overstory consisting mainly of redwood 16 (Sequoia sempervirens (D. Don) Endl.), Douglas fir (Pseudotsuga menziesii Mirb.), and western hemlock (Tsuga heterophylla (Raf.) Sarg.). The understory consists mainly of evergreen huckleberry (Vaccinium ovatum Pursh.), red huckleberry (Vaccinium parvifolium Smith) and salal (Gaultheria shallon Pursh.). It was logged approximately 85 years ago. 17 Figure 1. Aerial view of study area. NON, SE1/4, Sec. 28, T5N, R1E, H.M. (Humboldt County Photo HC-66, 18-29, flown by H.J. Chickering Jr. Corp., Eugene, Oregon, 1966) Scale: 1:13,200 Co
Figure 2. Map of NW1/4, SE1/4, Sec. 28, T5N, R1E, showing plot location and recording raingage distribution. R
TABLE #1 - Summary Description of Study Plots
ELEVATION
BASAL AREA R
BASAL AREAR
%R
TREER
LOCATION OF
ABOVE SEA R
ASPECT R
PLOT #R
PER PLOTR
PER ACRER
SPECIES R
SLOPE
R
RECORDING
RAINGAGE
R
LEVEL
(FT.)
(SQ.FT.)R
(SQ.FT.)R
234.88R
160R
5R
north-R
gages #1 and #2 are
1R
redwood R
46.97R
approximately 30'
eastR
south of plot #1
135R
0R
gage #3 is about 30
redwoodR
21.98R
109.92R
2R
feet southwest of
plots #2 and #3
westerly
3R
redwoodR
18.49R
92.46R
140R
5R
215.46 R
gage #4 is about 20
4R
redwoodR
43.11R
north-R
160R
7R
feet east of plots #4
eastR
and #5
179.71R
north5R
redwoodR
35.94R
180R
7R
east
R
V STUDY METHODS Interception by a forest canopy cannot be measured directly but may be arrived at by subtracting net rainfall from gross rainfall. In this study, net rainfall was determined by measuring only throughfall since stemflow was observed to be of an insignificant amount. This is due to the characteristic thick, fibrous bark of the redwood. Data were collected starting after the initial rain storm1, October 16, 1970 and finalized on the fifteenth storm, November 9, 1970. Fifteen storms were felt to be substantial for this study. The general procedure was to directly measure gross precipitation and throughfall. Intercep­
tion was then computed by subtracting from gross precipitation the amount of throughfall. Measurements were taken at five 1/5-acre plots. At each 1/5-acre plot, six trees were selected to combine dominant, co-dominant, and intermediate crown classes on each site. At each sample tree, a #10 "catch can" (see Figure #4, page 26) was placed at a distance of two feet from the bole of the tree. In the same direction another #10 can was placed at a distance of six feet from the bole. In plots #2 and #3 at trees #2 and #3, a #10 can was also placed at a distance of four feet from the tree bole. The following gives the plot, tree, and "throughfall can" distribution: TABLE #2 Tree no. and "throughfall can" distribution at distances from the tree bole. TREE 1R
PLOT #R
TREE 2R
TREE 3R
TREE 4R
TREE 5R
TREE 6
1
R
2'R
2
2'R
2'R
2'R
2' 6'R
6'R
6'R
6'R
6'R
6' 1 A storm is defined as a period of rainfall separated by six hours or more from another rainfall. 21 TABLE #2 (Continued) PLOT #R
TREE 1R
TREE 2R
TREE 3R
TREE 4R
TREE 5R
TREE 6
2
2'
4'
6'
2'
4'
6'
6'
2'
4'
6'
2'
4'
6'
2'
6'
2'
6'
2'
6'
2'
6'
2'
6'
3
4
5
2'
2'
2'
2'
6'
6'
6'
2'
2'
2'
6'
6'
6'
6'
2'
6'
2'
6'
2'
6'
2'
6'
2'
6'
2'
6'
2'
6'
Four recording raingages, each with an orifice of 8.00 inches were used to measure the gross precipitation. These gages were placed in the most convenient open sites as close as possible to the individual study plots. Figure #2, page 18, shows the exact position of the recording raingages in relation to the plots. Three of the raingages were the eight-day type and one was a 24­
hour type. Raingages were numbered as to their type and assigned to the following plots: Gage Number
1
2
3
4
Type
24-hour
8-day
8-day
8-day
Plot Number 1
1
2,3 4,5 After each rain the total depth at each "throughfall can" was recorded as was the amount of gross precipitation from the recording raingages. The total depth of gross precipitation was an average of the four recording gages. Condition of the canopy, i.e. amount of wetness; type of day, i.e. cloudy vs. sunny, and windyness were also 22 recorded after each storm. Chapter 6 gives the summary of individual rains investigated in the study. The appendix shows the individual rainfall measurements. At each individual plot, individual sample tree measurements were taken. The following summaries, by individual study plot, will describe the general characteristics of each sample tree. Photographs between pages 26 and 34 show "throughfall can" distribution, recording raingage set-ups, and relative canopy density taken from plot center. Figure #4, page 36; figure #8, page 30; figure #10, page 32; figure #11, page 33; and figure #12, page 34 show throughfall can distribution. Figure #6, page 28 and figure #9, page 31, show recording raingage set-ups. Figure #3, page 25; figure #5, page 27; and figure #7, page 28, show relative canopy density. PLOT #1 TREE #
CROWN CLASS
D.B.H.(IN)
CROWN LENGTH(FT)
TREE HT.(FT) 1
Co-dominant
25.8
62
112 2
Intermediate
16.1
50
80 3
Co-dominant
20.1
73
118 4
Intermediate
10.1
45
60 5
Dominant
35.8
65
125 6
Intermediate
10.0
33
68 Average
(54) 23 PLOT #2
TREE #
CROWN CLASS
D.B.H.(IN)
CROWN LENGTH(FT)
TREE HT.(FT)
1
Intermediate
10.2
35
60
2
Intermediate
17.8
30
50
3
Intermediate
9.8
35
50
4
Intermediate
7.7
35
50
5
Dominant
19.9
65
110
6
Co-dominant
17.9
45
70
Average
(41)
PLOT #3
TREE #
CROWN CLASS
D.B.H.(IN)
CROWN LENGTH(FT)
TREE HT.(FT)
1
Intermediate
10.6
35
70
2
Intermediate
6.4
30
60
3
Co-dominant
14.3
50
100
4
Dominant
32.1
45
125
5
Co-dominant
21.2
40
110
6
Co-dominant
14.1
45
95
Average
(41)
24 PLOT #4
TREE #
CROWN CLASS
D.B.H.(IN)
1
Co-dominant
15.9
45
100
2
Intermediate
6.5
45
75
3
Co-dominant
20.1
55
105
4
Dominant
35.9
60
140
5
Co-dominant
14.2
45
90
6
Dominant
28.9
50
120
Average
CROWN LENGTH(FT)
TREE HT.(FT)
(50)
PLOT #5
TREE #
CROWN CLASS
D.B.H.(IN)
CROWN LENGTH(FT)
TREE HT.(FT)
1
Intermediate
13.1
40
90
2
Co-dominant
24.2
45
110
3
Co-dominant
27.1
55
120
4
Intermediate
8.1
45
65
5
Dominant
30.1
45
130
6
Intermediate
14.3
40
80
Average
(45)
25 Figure 3. Relative canopy density for Plot #1. 26 Figure 4. #10 cans and location at 2 feet and 6 feet from tree bole on Plot #4. 27 Figure 5. Relative canopy density for Plot #2. 28 Figure 6.
Recording raingage set-up for
Plots #2 and #3.
29 Figure 7. Relative canopy density on Plot #4. 30
Figure 8. #10 can set-up at intervals of 2, 4, and 6 feet from tree bole on Plot #3. 31 Figure 9. Recording raingage set-up for Plot #1. 8-day gage .(left) 24-hour gage (right). 32 Figure 10. #10 can set-up and locale for Plot #5. 33 Figure 11. #10 can set-up on Plot #2. Figure 12. #10 can set-up and area of Plot #2. Note: red circles identify can locations. VI RESULTS AND DISCUSSION A total of fifteen rain storms were studied in which a total of 7.09 inches of rain fell. Table #3, page 38, gives the individual breakdown of each storm. Rainfall amounts ranged from a low of 0.05" for storm #14 to a high of 1.20" during storm #7. Rainfall intensities per hour for the 15 storms studied ranged from 0.05" per hour to 0.50 inches per hour. These rates are the average for the entire storm duration. The number of days since the previous storm were recorded to relate the amount of interception and net throughfall that were a function of a previous storm. Throughfall In the study net throughfall percentages ranged from a low of 60.4% at 2 feet from the tree bole to a high of 82.8% at 6 feet from the bole. These values are the average percentages for the entire 15 storms at the particular distance from the tree bole. Averages for each individual rainfall at each "throughfall can" distance are also given. These net throughfall percentages for each storm ranged from a low of 18.4% to a high of 84.4%. The depth in inches of net throughfall ranged from a total average low of 4.28 inches on plot number one at the two-foot distance to a high of 5.87 inches on plot number three at the six-foot interval. Tables #4 and #5, pages 39 and 40, give the net throughfall summary in inches and percentages, respectively. Both net throughfall and interception were found to be linear functions of the amount of rain per storm. The formulae used in this investigation are as follows: 36 Where: a = Y - intercept value at X = 0 b = tangent or slope of regression line r XY = correlation coefficient of Y with X Y = a + bX = linear regression equation n = number of paired values X = value of independent variable = inches of rain per storm Y = value of dependent variable = net throughfall or net interception in inches per storm EX = sum of X values c X2 = sum of squares of X values (LX) 2 = sum of X values squared (f Y) 2 = sum of Y values squared = sum of squares of Y values = sum of Y values XY = sum of cross products of paired X and Y values Equations were developed for the distance of two, four, and six feet from the tree bole. The equations are as follows: 37 1. At a distance of two feet from the tree bole, net throughfall in inches equals 0.7174X - 0.0223, with a correlation coefficient of 0.9987. 2. At a distance of four feet from the tree bole, net throughfall in inches equals 0.7396X + 0.0240, with a correlation coefficient of 0.9836. 3. At a distance of six feet from the tree bole, net throughfall in inches equals 0.6810X + 0.0809, with a correlation coefficient of 0.8463. Figure #13, page 41, shows this linear relationship of net through-
fall with gross rainfall at the various distances from the tree bole. An average net throughfall linear regression equation was developed for all rainstorms at all distances within the tree canopy. This equation is: 0.7126X + 0.0275, with a correlation coefficient of 0.9817. Figure #14, page 43, shows this relationship. It was found that all correlation coefficients were significant (Critical Values for Correlation Coefficients, Table Y, pp. 224-226, Statistical Tables by Rohlf and Sokal). It can be seen that the differences between the equations at the different tree bole distances are slight. There was, however, a definite increase in net throughfall as the distance from the tree bole increased. Figure #13, page 41, shows this relationship in a linear regression form. Figure #15, page 44, shows this relationship in the non-linear form. 38 TABLE #3 - Rainfall Summary - Gross Throughfall Time Since
PreviousR
Remarks
Rainstorm
Storm
#
Total
Depth
(In.)
Intensity*
(In./Hr.)
Date of
Rainstorm
1
0.15
0.15
10/16/70
InitialR
Cold, cloudy, no stemStormR
flow
2
0.10
0.10
10/18/70
2 daysR
Cold, cloudy, very wet
area, no stemflow
3
1.00
0.25
10/19/70
Cold, cloudy, windy,
1 dayR
no stemflow
4
0.38
0.09
10/21/70
2 daysR
Cold, cloudy, canopy
wet, no stemflow
5
0.97
0.19
10/23/70
2 daysR
Cold, cloudy, windy,
no stemflow
6
0.07
0.07
10/25/70
Canopy wet from storm
2 daysR
#6, no stemflow
7
1.20
0.22
10/25/70
7 hoursR
Clear, sunny, canopy
drying quickly, no
stemflow
8
0.11
0.22
10/26/70
1 dayR
Clear, cold, no stemflow
9
0.10
0.10
10/30/70
4 daysR
Cloudy, cold, canopy
wet, no stemflow
10
0.30
0.50
10/30/70
8 hoursR
Cloudy, cold, very
windy, no stemflow
11
0.96
0.24
11/ 2/70
3 daysR
Cold, cloudy, slight
breeze, no stemflow
12
0.18
0.09
11/ 3/70
1 dayR
Sunny, clear, windy,
no stemflow
13
1.05
0.35
11/ 5/70
Cold, low clouds, slight
2 daysR
breeze, no stemflow
14
0.05
0.05
11/ 6/70
low clouds, calm,
1 dayR
Cold,R
no stemflow
15
0.46
0.15
11/ 9/70
Cold, cloudy, foggy,
3 daysR
very wet, no stemflow
Total
7.09
*Average for entire storm duration TABLE #4 - Rainfall Summary - Net Throughfall (Inches) Plot # and distance from tree bole (feet) PLOT #1
R R
R
R
R
PLOT #2
PLOT #3
PLOT #4
PLOT #5
AVERAGES t
Storm
#
2'
6'
2'
4'
6'
2'
4'
6'
2'
6'
2'
6'
2'
4'
6'
1
0.09
0.11
0.11
0.11
0.12
0.10
0.10
0.11
0.09
0.10
0.09
0.10
0.06
0.10
0.10
2
0.07
0.07
0.08
0.07
0.08
0.08
0.07
0.08
0.07
0.08
0.07
0.08
0.07
0.07
0.08
3
0.67
0.71
0.73
0.75
0.83
0.74
0.75
0.83
0.67
0.75
0.68
0.78
0.69
0.75
0.68
4
0.17
0.24
0.24
0.27
0.30
0.27
0.30
0.31
0.20
0.24
0.21
0.25
0.21
0.29
0.27
5
0.58
0.66
0.75
0.73
0.83
0.80
0.80
0.85
0.63
0.74
0.66
0.75
0.68
0.76
0.76
6
0.01
0.01
0.03
0.03
0.04
0.04
0.04
0.05
0.01
0.02
0.01
0.02
0.02
0.04
0.03
7
0,86
0.92
0.90
0.92
0.94
0.90
0.90
0.96
0.86
0.93
0.87
0.92
0.88
0.91
0.93
8
0.07
0.08
0.08
0.08
0.08
0.08
0.08
0.09
0.07
0.08
0.08
0.09
0.08
0.08
0.09
9
0.07
0.07
0.08
0.08
0.09
0.08
0.08
0.09
0.07
0.07
0.07
0.08
0.07
0.08
0.08
10
0.13
0.16
0.18
0.19
0.22
0.19
0.21
0.24
0.14
0.17
0.15
0.17
0.16
0.20
0.19
11
0.57
0.63
0.71
0.74
0.80
0.79
0.80
0.83
0.60
0.70
0.60
0.71
0.65
0.77
0.73
12
0.11
0.13
0.14
0.14
0.15
0.14
0.14
0.15
0.11
0.13
0.12
0.13
0.12
0.14
0.14
13
0.68
0.74
0.75
0.78
0.84
0.75
0.80
0.83
0.69
0.74
0.70
0.79
0.71
0.79
0.79
14
0.01
0.01
0.01
0.02
0.02
0.02
0.03
0.03
0.01
0.01
0.01
0.01
0.01
0.03
0.02
15
0.20
0.25
0.34
0.36
0.40
0.37
0.38
0.42
0.21
0.27
0.25
0.29
0.27
0.37
0.33
Total
(In.)
4.28
4.78
5.13
5.26
5.74
5.35
5.48
5.87
4.43
5.03
4.56
5.17
Total
(%)
60.4
67.5
72.3
74.2
81.0
75.4
77.4
82.8
62.5
70.9
64.4
72.9
TABLE #5 - Rainfall Summary - Net Throughfall (Percent of gross rainfall) Plot # and distance from tree bole (feet) PLOT #1
R R
R
R
R
PLOT #4
PLOT #2
PLOT #3
PLOT #5
AVERAGES V
Storm # 2'
6'
2'
4'
6'
2'
4'
6'
2'
6'
2'
6'
2'
4'
60.0
73.3
73.3
73.3
80.0
66.6
66.6
73.3
60.0
66.6
60.0
66.6
63.9
69.9
71.9 2
70.0
70.0
80.0
70.0
80.0
80.0
75.0
80.0
70.0
80.0
70.0
80.0
74.0
72.5
78.0 3
67.0
63.1
73.0
75.0
83.0
74.0
75.0
83.0
67.0
75.0
68.0
78.0
69.8
75.0
78.0 4
44.7
67.7
63.1
71.0
78.9
71.0
78.9
81.6
52.6
63.1
55.2
65.8
57.3
74.9
70.5 5
59.4
62.3
76.9
74.8
85.1
82.1
82.1
87.2
64.6
75.9
67.7
76.9
70.1
78.4
78.5 6
10.6
12.5
37.5
37.5
50.0
50.0
50.0
62.5
12.5
25.0
12.5
25.0
24.6
43.7
35.0 7
71.6
72.7
75.0
76.6
78.3
75.0
75.0
80.0
71.6
77.5
72.5
76.6
73.1
75.8
77.8 8
63.6
70.0
72.7
72.7
72.7
72.7
72.7
81.8
63.6
72.7
72.7
81.8
69.0
72.7
76.3 1
6'
9
70.0
53.3
80.0
80.5
90.0
80.0
80.0
90.0
70.0
70.0
70.0
80.0
74.0
80.2
80.0 10
43.3
65.6
60.0
63.3
73.3
63.3
70.0
80.0
46.7
56.7
50.0
56.7
52.6
66.6
64.0 11
59.4
72.2
73.9
77.1
83.3
82.2
83.3
83.3
62.5
72.9
62.5
73.9
68.1
80.2
75.8 12
61.1
70.4
77.7
77.7
83.3
77.7
77.7
83.3
61.1
72.2
66.7
72.2
68.8
77.7
76.6 13
64.7
70.4
71.4
74.2
80.0
71.4
76.2
79.0
65.7
70.4
66.6
75.2
67.9
75.2
75.0 14
10.0
16.0
20.0
40.0
40.0
40.0
60.0
60.0
11.0
20.0
11.0
20.0
18.4
50.0
31.2 15
43.4
54.3
73.9
78.2
86.9
80.4
82.6
91.3
45.6
58.7
54.3
63.0
59.5
80.4
70.8 41 Figure 13. Linear regression comparing net throughfall with gross rainfall at distances of 2, 4, and 6 feet from the tree bole. 42 The difference in the amount of net throughfall at the various distances is due to the increased amount of biomass closer to the bole of the tree. The equations show that as the distance from the bole increases, the amount of net throughfall also increases. Figure #13, page 41, shows that the linear regression equation for the six-foot distance intersects the linear equation at the two-
and four-foot distances. This is probably due to the fact that at the edge of the tree canopy, theoretically there is no interception and at this point net throughfall equals gross rainfall. This would be highly unlikely in a stand condition, because the tree would have to be completely undisturbed by the canopies of the surrounding trees. The linear graphs show that for each inch of gross rainfall, about 70% becomes net throughfall. At higher amounts this relationship would hold fairly constant. Net throughfall was also correlated to crown length and although no significant correlation was developed, it was generally found that with an increase in crown length there is a decrease in net throughfall. This can be understood by the fact that the greater the crown length, the greater the amount of foliage, thus increasing the interception storage potential. Net throughfall was related to crown position, and it was found that with the dominant trees, the interception storage potential was greater. The greatest amount of net throughfall occurred under trees of intermediate crown class. This is probably a function of redistri­
bution of rainfall from large trees to smaller trees. Net throughfall was related to storm intensity and it was found that with an increase in rainfall intensity, the net throughfall per­
centage increases also, but very gradually and thus seems to be more 43 Figure 14. Linear regression comparing average net throughfall with gross rainfall at all distances from the tree bole. 44 Figure 15. Net throughfall (inches) in relation to gross rainfall at distances of 2, 4, and 6 feet from the tree bole. 45 dependent upon rainfall amount rather than intensity on an hour basis. This is variable depending upon the length of time between rainfalls, wetness of the canopy, windyness, and the transpiration rate on the given day. It was observed that the maximum amount of interception occurred when the period between storms was the longest. This is due to the fact that the canopy has a chance to dry out, thus increasing the potential storage capacity of the leaf. No correlation could be developed with net throughfall and temperature and wind velocity, but it is believed that a combination of warmer air temperatures, high wind velocities, and long periods between rainfall greatly reduce the amount of net throughfall. Net throughfall (expressed as a percentage of gross rainfall) is compared to gross rainfall in Figure #16, page 46. It was found that with rainfalls of very low amounts, there is also a very low percentage of net throughfall. This can be seen in Table #5, page 40, for storm #14. The amount for this storm was 0.05 inches and the net throughfall at the 2-foot tree bole distance was only 18.4%. Individual #10 can measurements on plots number 1 and 4 show only trace measurements during this rainfall (Appendix, pages 97 and98 ). These two plots also had the greatest amount of dominant and co-dominant trees, showing again the affect of crown position on net throughfall potential. As the amount of rainfall increases the net throughfall also increases. When the amount reaches 0.2 inches, about 40% is accounted for as net throughfall. The curve then levels off at about 75% net throughfall for rainfalls of higher amounts. There is still a gradual increase, but a very negligible amount. This can be seen in Table #4, page 39, where the highest average net throughfall amount was 82.8%. 46 Figure 16. Net throughfall (percent) in relation to gross rainfall (inches). 47 Finally, net throughfall was compared to basal area per acre. Figure #17, page 48, shows this possible relationship. It is suspected that with an increase in basal area per acre, there is a decrease in the percentage of net throughfall. In this investigation basal area per acre ranged from a low of 92.4 square feet to a high of 234.9 square feet on plots #3 and #1 respectively. The percentage of net throughfall ranged from 82.8% on plot #3 to 60.4% on plot #1. Table #8, page 51, summarizes these data. Since the study plots were closely clustered, there was no significant difference in rainfall due to elevational differences and aspect changes. Interception Since no stemflow was observed during the study, interception was simply the difference between gross rainfall and net throughfall. For the total of 15 study storms, interception percentages ranged from an average high of 36.9% to an average low of 17.2%. Tables #6 and #7, pages 49 and 50, summarize the interception data obtained. For individual storm measurements interception ranged from 100% to 10% (see individual storm measurements pages 71 - 100 Appendix). Interception was also found to be a linear function of the amount of rain per storm. The same formulae (page 36) were used as in net throughfall to develop these linear equations. Equations were developed at the three tree bole distances of two, four, and six feet. The equations are as follows: 1. At a distance of two feet from the tree bole, interception in inches equals 0.2826X + 0.0190, with a correlation coefficient of 0.9814. 48 Figure 17. Average net throughfall per plot in relation to basal area per acre. TABLE #6 - Rainfall Summary - Interception (Inches) Plot # and distance from tree bole (feet) PLOT #1
RR
R
R
R
PLOT #2
PLOT #3
PLOT #5
AVERAGES PLOT #4
Storm
#
2'
6'
2'
4'
6'
2'
4'
6'
2'
6'
2'
6'
2'
4'
6'
1
2
.06
.03
.04
.03
.04
.02
.04
.03
.03
.02
.05
.02
.05
.025
.04
.02
.06
.03
.05
.02
.06
.03
.05
.02
.05
.02
.045
.027
.04
.02
3
4
5
6
7
8
9
10
11
12
13
14
15
.33
.21
.395
.067
.34
.04
.03
.17
.39
.07
.37
.045
.26
.29
.14
.315
.065
.28
.03
.03
.14
.33
.05
.31
.042
.21
.27
.14
.225
.045
.30
.03
.02
.12
.25
.04
.30
.04
.12
.25
.11
.245
.045
.28
.03
.015
.11
.22
.04
.27
.03
.10
.17
.08
.145
.035
.26
.025
.01
.08
.16
.03
.21
.03
.06
.26
.11
.175
.035
.30
.03
.02
.11
.17
.04
.30
.03
.09
.25
.08
,175
.035
.30
.03
.02
.09
.16
.04
.25
.02
.08
.17
.07
.170
.025
.24
.02
.01
.06
.13
.03
.22
.02
.04
.33
.18
.345
.065
.34
.035
.03
.16
.36
.07
.36
.044
.25
.25
.14
.235
.055
.27
.03
.03
.13
.26
.05
.31
.04
.19
.32
.17
.315
.065
.33
.03
.03
.15
.36
.06
.35
.044
.21
.22
.13
.225
.055
.28
.02
.02
.13
.25
.05
.26
.04
.17
.30
.16
.291
.055
.32
.033
.02
.14
.30
.05
.33
.040
.18
.25
.09
.210
.040
.290
.030
.017
.10
.19
.04
.26
.025
.09
.22
.11
.218
.047
.26
.025
.02
.10
.22
.04
.26
.034
.13
2.807
2.302
1.960 1.830
1.345
1.740
1.605
1.220
2.659
2.060
2.524
1.920
7 . 090" 39.59
32.46
27.64 25.81
18.97
24.54
22.63
17.21
37.50
29.05
35.59
27.08
TABLE #7 - Rainfall Summary - Interception (percent of gross rainfall) Plot # and distance from tree bole (feet) PLOT #1
Storm
#
R
R
R
R
R
PLOT #2
PLOT #3
PLOT #4
PLOT #5
AVERAGES 2'R
6'
2'R
4'R
6'
2'R
4'
6'
2'
6'
2'
6'
2'
4'
6'
40.0
30.0
33.4
20.0
40.0
30.0
33.4
20.0
36.0
26.0
30.1
27.5
28.1
22.0
3
4
5
6
7
8
26.7R
20.0
26.7R
33.4R
40.0R
26.7
33.4 26.7
30.0R
30.0R
30.0
20.0R
20.0
20.0R
25.0 20.0
29.0
27.0R
25.0R
17.0
33.0R
26.0R
25.0 17.0
55.3R
36.9
36.9R
29.0R
21.1
29.0R
21.1 18.4
40.6R
32.3
23.1R
25.2R
14.9
17.9R
17.9 12.8
89.4R
87.5
62.5R
62.5R
50.0
50.0R
50.0 37.5
21.7
25.0R
25.0 80.0
28.4R
23.4
25.0R
23.4R
27.3
27.3R
27.3 18.2
36.4R
27.3
27.3R
27.3R
33.0
47.4
35.4
87.5
28.4
36.4
25.0
36.9
24.1
75.0
22.5
27.3
32.0
44.8
32.3
87.5
27.5
27.3
22.0
34.2
23.1
75.0
23.4
18.2
30.1
42.6
29.8
75.3
26.8
30.9
25.0
25.1
21.6
56.3
24.2
27.3
22.0
29.5
21.5
65.0
22.2
23.7
9
30.0R
30.0
20.0R
19.5R
10.0
20.0R
20.0 10.0
30.0
30.0
30.0
20.0
26.0
19.8
20.0
10
11
56.746.740.036.726.736.730.0 20.0
53.3
4
37.5
26.1R
22.9R
16.7
17.8R
16.7
16.7
40.6R
34.4
43.3
27.1
50.0
37.5
43.3
26.1
47.3
31.9
33.4
19.8
36.0
24.2
12
38.9
22.3R
22.3R
16.7
22.3R
22.3 16.7
38.9R
27.8
27.8
33.3
27.8
31.1
22.3
23.4
13
14
20.0
28.6R
23.8 21.0
25.8R
34.3
29.6
28.6R
35.3R
89.0
80.0R
60.0R
60.0
60.0R
40.0 40.0
90.0R
84.0
29.6
80.0
33.4
89.0
24.8
80.0
32.0
81.6
24.8
50.0
25.0
68.8
15
26.1R
21.8R
13.1
19.6R
17.4
8.7
56.6R
45.7
54.4
1
41.3
45.7
37.0
40.5
19.6
29.2
1
2
1
51 TABLE #8 Net Throughfall Summary Net throughfall percentages with basal area per acre for each study plot. PLOT #
DISTANCE FROM TREE BOLE (Feet)
2'
4'
BASAL AREA/ACRE 6'
(SQ.FT.) 67.54%
234.88 1
60.41%
2
72.36%
74.19%
81.03%
109.92 3
75.46%
77.37%
82.79%
92.4 4
62.50%
70.95%
215.46 5
64.41%
72.92%
179.71 52 2. At a distance of four feet from the tree bole, interception in inches equals 0.2242X + 0.0076, with a correlation coefficient of 0.9872. 3. At a distance of six feet from the tree bole, interception in inches equals 0.2154X - 0.0345, with a correlation coefficient of 0.9901. Figure #18, page 53, shows the relationship of interception with gross rainfall. An average equation for this linear relationship for all storms (7.09 inches) and at all distances within the tree canopy was developed. The equation is: 0.2227X - 0.0153, with a correlation coefficient of 0.9862. Figure #19, page 54, shows this relationship. The Y-intercept value in this average equation shows that with a small amount of rain there is an immediate interception value. The negative intercept is simply due to the chance variations in the statistics and also fitting a straight line to what may really be a curvilinear relation. The slope of the equation indicates that as the gross rainfall increases, the amount of interception also increases, but at a much slower rate. This is due to the fact that usually before a rain, the canopy of the tree is dry and can hold almost all of the precipitation at first contact. As the foliage becomes wetter, the water holding capacity decreases, thus the interception potential levels off and will eventually reach a maximum water holding capacity. Additional rainfall will result in runoff from the foliage and thus create throughfall. Interception was also found to be a linear function of crown length. Equations for this relationship were developed for distances of two and six feet from the tree bole. The equations are as follows: 53 Figure 18. Linear regression comparing interception with gross rainfall at distances of 2, 4, and 6 feet from the tree bole. 54 Figure 19. Linear regression comparing average interception with gross rainfall at all distances from the tree bole. 55
1. At a distance of two feet from the tree bole, interception in inches equals 0.0690X - 0.0850, with a correlation coefficient of 0.9165. 2. At a distance of six feet from the tree bole, interception in inches equals 0.0727X - 0.0155, with a correlation coefficient of 0.9463. Again it was found that all correlation coefficients were significant (Critical Values for Correlation Coefficients, Table Y, pages 224-226, Statistical Tables by Rohlf and Sokal). The difference between these last two equations is that as the distance from the tree bole increases, the interception potential decreases. Figure #20, page 56, shows this linear relationship of crown length with interception. It was found that interception increases with an increase in crown length, but the change is very slow. For example, with the total interception of all 15 storms, an increase in crown length of 40 feet increased the interception amount 0.2 inches. This relationship also shows the importance of crown position with inter­
ception. It was observed that with the dominant crown class trees, the interception amount was greater than with the intermediate class. Interception was related to rainfall intensity and it was found that as the intensity of the rainfall increased, the interception amount decreased, but again as in throughfall this relationship seems to be more dependent upon amount of rainfall rather than intensity. Interception has been frequently expressed as a percentage of total rainfall. Figure #21, page 58, shows this relationship. The very high interception percentages are correlated with the very low amounts of rainfall. 56 Figure 20. Linear regression comparing average interception with average crown length/plot at 2 and 6 feet from the tree bole. 57 Actually the amount intercepted from light showers is of little significance because even if it did reach the ground, it would have negligible effect on soil moisture. In fact, during the growing season, a few hundredths of an inch on the foliage is more helpful to the trees than the same amount applied to the soil (Hoover, M.D., 1953). Wetting the leaves serves to reduce transpiration rates and during periods of soil moisture stress, this may be of considerable benefit. Interception rates were compared to basal area per acre (Figure #22, page 59) as a possible relation, and it is suspected that with an increase in basal area per acre, there is also an increase in the inter­
ception amounts. Although the data is inconclusive, it is suspected that this is a curvilinear relationship. In plot #3 where basal area per acre was the lowest at 92.4 square feet, the interception rates were also the lowest, ranging from 24.5% at two feet from the bole to 17.2% at six feet from the bole. In plot #1 where basal area per acre was the highest at 234.9 square feet, the interception amounts were also the highest, ranging from 39.6% at two feet from the bole to 32.5% at six feet from the bole. Table #9, page 61, summarizes this relationship. Figure #23, page 60, shows the relationship of interception over gross rainfall at the various distances from the tree bole. The difference in the results of the various equations was slight, but a definite trend did develop. In general, it was found that with net throughfall, as the distance from the tree bole increased, the amount of net throughfall increased also. With interception it was found that as the distance from the tree bole increased, the amount of interception decreased. These inverse relationships are expected. Net throughfall and interception values are compared by a bar graph in Figure #24, page 62. 58 Figure 21. Interception (percent) in relation to gross rainfall (inches). 59 Figure 22. Average interception per plot in relation to basal area per acre. 60 Figure 23. Interception (inches) in relation to gross rainfall at distances of 2, 4, and 6 feet from tree bole. 61 TABLE #9 Interception Summary Interception percentages with basal area per acre for each study plot. PLOT #
DISTANCE FROM TREE BOLE (Feet)
2'
4'
BASAL AREA/ACRE 6'
(SQ.FT.) 32.46%
234.88 1
39.59%
2
27.64%
25.81%
18.97%
109.92 3
24.54%
22.63%
17.21%
92.4 4
37.50%
29.05%
215.46 5
35.59%
27.08%
179.71 VII SUMMARY AND CONCLUSIONS Interception losses and net throughfall were compared with gross rainfall in a second growth redwood (Sequoia sempervirens (D. Don) Endl.) stand. The investigation studied 15 storms beginning on October 16, 1970 and ending November 9, 1970. The study was conducted in the NW1/4, SE1/4, Section 28 of Freshwater Forest. Five study plots were used, each containing six sample trees. Basal area per acre ranged from a high of 234.9 square feet on plot #1 to a low of 92.4 square feet on plot #3. Standard #10 cans were used at each sample tree to collect net throughfall. The cans were set at distances of two and six feet from the tree bole. On plots #2 and #3, on sample trees #2 and #3, #10 cans were also set four feet from the tree bole. Four recording raingages were used to measure gross rainfall. They were placed in open areas near the study plots. After each rain, the cans were measured and the charts read. Conditions and possible changes in the study plots were noted. Linear regression equations were developed for interception and net throughfall as a function of gross rainfall at the various distances from the tree bole. Correlation coefficients were determined to test the accuracy of the equations. The linear functions for net throughfall in inches at the various distances from the tree bole and their respective correlation coefficients are as follows: at 2' -R-R
0.0223, r = 0.9987
0.7174X
0.0240,
=
0.9836 at 4' - 0.7396X +Rr
at 6' - 0.6810X + 0.0809, r = 0.8463 64 An average net throughfall equation in inches for all distances within the canopy was developed. The equation is: 0.7126X + 0.0275, r = 0.9819 It was found that: 1. Net throughfall ranged from 60.4% to 82.8% of gross rainfall. 2. Net throughfall has a maximum average of about 75% of gross rainfall. 3. Net throughfall is very low at small amounts of rainfall. 4. Net throughfall increases with the intensity of the storm, but is more dependent upon amount of rainfall. 5. Net throughfall seems to decrease with an increase in basal area per acre. 6. Net throughfall decreases with an increase in crown length. 7. Net throughfall increases with an increase in distance from the tree bole. 8. Net throughfall varies with crown position in canopy. Linear regression equations were computed for interception in inches as a function of the amount of rainfall. The equations at the various distances from the tree bole with their respective correlation coeffi­
cients are as follows: at 2' - 0.2826X + 0.0190, r = 0.9814 at 4' - 0.2240X + 0.0076, r = 0.9872 at 6' - 0.2154X - 0.0345, r = 0.9901 A linear equation for interception in inches at all distances within the canopy was also developed. The equation is: 0.0227X - 0.0153, r = 0.9862 65 Linear regression equations were computed for interception in inches as a function of crown length. Equations were developed at distances of two and six feet from the tree bole. The equations are: atR
2' - 0.0690X - 0.0850, r = 0.9165
at 6' - 0.0727X -R
0.1558, r = 0.9463
It was also found that: 1. Interception ranged from 17.2% to 36.9% of gross rainfall. 2. Percent interception is high at low intensities and decreases with high intensities, but total storm amount seems to be a governing factor. 3. Interception seems to increase with an increase in basal area. 4. Interception increases with an increase in crown length. 5. Interception has a maximum average of about 27% of gross rainfall. 6. Interception is correlated to time intervals between rainfalls. 7. Interception decreases with an increase in distance from the tree bole. 8. Interception varies with crown position. From the results of the study, the following comments and recom­
mendations for future studies of this nature are made: 1. Study plots should have a wide range of basal areas, crown classes, and age classes. 2. "Throughfall cans" should be flat on the bottom for easy measurement of volume by a depth gage. 3. Recording raingages should be in open areas. 4. More research should be done on the water holding capacities of the foliage of the redwood species. 66 5. Wide ranges of slope percents, elevations, and aspects should be used for study. 6. Other climatic data, such as wind velocity, temperature, and precipitation/evaporation ratios should be gathered and studied in relation to interception and throughfall data. LITERATURE CITED Beall, H. W. 1934. The penetration of rainfall through hardwood and softwood canopy. Ecology, 15:412-415. Boggess, W. R. 1956. Amount of throughfall and stemflow in a shortleaf pine plantation as related to rainfall in the open. Illinois Acad. Sci. Trans., 48:55-61. De Walle, D. R. and L. R. Paulsell. 1969. Canopy interception, stem-
flow and streamflow on a small drainage in the Missouri Ozarks. Univ. of Mo., College Agri. Expt. Sta., 1:1-26. Dunford, E. G. and C. H. Niederhof. 1944. Influence of aspen, young lodgepole pine, and open grassland types upon factors affecting wateryield. Journal of Forestry, 42:673-677. Gilbert, G. E. 1953. Rainfall interception by relatively undisturbed deciduous forests in Central Idaho. Doctorate dissertation, Ohio State University. Hamilton, E. L. and P. B. Rowe. 1949. Rainfall interception by chaparral in California. Calif. Dept. Nat. Resources, Div. of Forestry, 1:1-43. Helvey, J. D. 1967. Rainfall interception by hardwood forest litter in the Southern Appalachians. Southern Forest Expt. Sta., U. S. Forest Service, Res. Paper, SE-8. Helvey, J. D. and J. H. Patric. 1965. Canopy and litter interception by hardwoods. Water Resources Research, 1:193-206. Hirata, T. 1929. Contributions to the problem of the relations between the forest and water in Japan. Imp. Forestry Exp. Sta., 92:1-41. Hoover, M. D. 1953. Interception of rainfall in a young loblolly pine plantation. Southeastern Forest Expt. Sta., North Carolina, 21:1-13. Hoppe, E. 1896. Regenmessung unter baumkronen. (Translation in U. S. Dept. Agri. Library) Mitt. Forsth. Versuchsn. Osterr., 21:1-75. Horton, R. E. 1919. Rainfall interception. Mo. Weather Rev., 47:603-623. Kittredge, J. 1948. Forest influences. McGraw-Hill Book Company, Inc., New York, N.Y. Kittredge, J., H. J. Loughead, and A. Mazurak. 1941. Interception and stemflow in a pine plantation. Journal of Forestry, 39:505-522. 68 Laws, J. O. 1941. Measurement of the fall-velocities of water drops and raindrops. U. S. Conservation Service, 1:1-33. Lawson, E. R. 1967. Throughfall and stemflow in a pine-hardwood stand in the Ouachita Mountains of Arkansas. Southern Forest Expt. Sta., U. S. Forest Service, 3:1-26. Leonard, R. E. 1961. Interception of precipitation by northern hard­
woods. U. S. Forest Service, Northeastern Forest Expt. Sta., 59:1-16. Leyton, L., E. R. C. Reynolds, and F. B. Thompson. 1967. Rainfall interception in forest and moorland. International Symposium on Forest Hydrology, 90:163-178. Linsley, R. K. Jr., M. A. Kohler, and J. L. Paulhus. 1949. Applied hydrology. McGraw-Hill, New York, N.Y. Lunt, H. A. 1934. Distribution of soil moisture under forest trees. Journal Agri. Research, 49:695-703. Mitchell, J. D. 1930. Interception of rainfall by the forest. Journal of Forestry, 28:101-102. Monninger, L. V. 1950. Rainfall interception by aspen and herbaceous vegetation. U. S. Forest and Range Experiment Station, Ogden, 27:70-74. Munn, R. E. 1961. Energy budget and mass transfer theories of evapo-
ration. Proc. Hydrol. Symposium, Dept. of Northern Affairs and Nat. Res. Ottawa, Canada, 2:8-27. Munns, E. N. 1917. Studies of forest influences in California. Manuscript in the files of the U. S. Forest Service, Pacific Southwest Range and Expt. Sta., Berkeley, Calif. Ovington, J. D. 1956. A comparison of rainfall in different woodlands. The Journal of the Society of Foresters of Great Britain, 27:40-53. Patric, J. H. 1966. Rainfall interception by mature coniferous forests of southeast Alaska. Journal of Soil Water Conservation, 21:229-231. Pearson, G. A. 1913. A meteorological study of parks and timbered areas in the western yellow pine forests of Arizona and New Mexico. Monthly Weather Rev., 41:1615-1629. Reynolds, E. R. C. and L. Leyton. 1963. Measurement and significance of throughfall in forest stands. Blackwell Scientific Publications, 2:127-141. Rogerson, T. L. and W. R. Byrnes. 1968. Net rainfall under hardwood and red pine in Central Pennsylvania. Water Resources Research, 4:1-2. 69 Rothacher, J. 1963. Net precipitation under a Douglas-fir forest. Forest Science, 9:423-429. Rowe, P. B. 1948. Influence of woodland chaparral on water and soil in Central California. Calif. Dep. Nat. Resources, Div. of Forestry, 67:1-70. Rowe, P. B. and T. M. Hendrix. 1951. Interception of rain and snow by second-growth ponderosa pine. American Geophysical Union, 32:1-6. Rutter, A. J. 1963. Studies in the water relations of scotch pine in plantation conditions, 1. Measurement of rainfall and inter­
ception. Journal of Ecology, 51:191-203. Semago, W. J. and A. J. Nash. 1962. Interception of precipitation by a hardwood forest floor in the Missouri Ozarks. Univ. of Mo. Agri. Expt. Sta. Res. Bull., 796. Sims, I. H. 1932. Litter decomposition and accumulation in the pine oak type of the Southern Appalachians. Journal of Forestry, 30:90-91. Skau, C. M. 1964. Interception, throughfall, and stemflow in Utah and alligator juniper cover types of Arizona. Forest Science, 10:283-287. Trimble, J. R. Jr., and Weitzman, S. 1954. Effect of a hardwood forest canopy on rainfall intensities. American Geophysical Union, 35:226-234. Voigt, J. K. 1960. Distribution of rainfall under forest stands. Forest Science, 6:2-9. Wicht, C. L. 1941. An approach to the study of rainfall interception by forest canopies. Journal of South African Forestry, 6:1-70. Zinke, P. J. 1967. Forest interception studies in the United States. International Symposium on Forest Hydrology, 92:137-161. Zon, R. 1927. Forest and water in the light of scientific investigation. U. S. Natl. Waterways, Final Report. Senate Doc. 469, 62nd Congress, 2nd Session, V:205-302. APPENDIX 71
TABLE A-1
Storm #1 (net throughfall in inches)
October 16, 1970
Depth: 0.15"
Intensity: 0.15"/hr.
Inches
Inches
@R
2'
@R
4'
Inches
@R
6'
Plot #1
Tree #1
0.08
0.10
2
0.10
0.12
3
0.11
0.12
4
0.09
0.10
5
0.11
0.11
6
0.10
0.11
X=
0.09
X = 0.11
Plot #2
Tree #1
0.10
2
0.11
0.11
0.12
3
0.09
0.09
0.10
4
0.12
0.13
5
0.12
0.13
6
0.11
0.12
0.11
=R
0.11
= 0.11
5R
=R
0.12
Plot #3
Tree #1
0.10
2
0.10
0.11
0.12
3
0.10
0.10
0.10
4
0.12
0.12
5
0.12
0.12
6
0.10
0.11
X = 0.10
0.10
=�
0.10
5: =R
0.11
72 TABLE A-1R
(Continued) Inches
@R
2'
InchesR
Inches
@R
4'R
@R
6'
Plot #4
Tree #1
0.07
0.08
2
0.09
0.09
3
0.10
0.10
4
0.09
0.10
5
0.11
0.11
6
0.10
0,10
7 = 0.09
3
0.10
=�
Plot #5
Tree #1
0.08
0.09
2
0.09
0.10
3
0.10
0.10
4
0.10
0.11
5
0.10
0.11
6
0.09
0.10
7 = 0.09
Remarks: Cold, cloudy day
I
=
0.10
73 TABLE A-2
Storm #2R
(net throughfall in inches)
October 18,R
1970
Depth:R
0.10"
Intensity:R
0.20"/hr.
Inches
Inches
@R
2'
@R
4'
Inches
@R
6'
Plot #1
Tree #1
0.07
0.09
2
0.08
0.06
3
0.06
0.07
4
0.07
0.08
5
0.07
0.09
6
0.06
0.07
=R
0.07
X = 0.07
Plot #2
Tree #1
0.09
2
0.08
0.08
0.08
3
0.06
0.06
0.06
4
0.09
0.09
5
0.09
0.09
6
0.08
0.08
0.08
=�
0.09
=R
0.07
= 0.08
Plot #3
0.09
Tree #1
0.09
2
0.09
0.09
0.09
3
0.06
0.06
0.07
4
0.09
0.09
5
0.09
0.09
6
0.08
0.09
X = 0.08
= 0.075
I = 0.08 74 TABLE A-2 (Continued) Inches
@R
2'
Inches
@R
4'
Inches
@R
6'
Plot #4
Tree #1
0.08
0.09
2
0.09
0.10
3
0.06
0.07
4
0.06
0.07
5
0.07
0.07
6
0.06
0.07
X = 0.07
X = 0.08
Plot #5 Tree #1
0.08
0.09 2
0.08 0.09 3
0.06 0.07 4
0.07 0.07 5
0.07 0.08 6 0.06
0.07 X = 0.07
X = 0.08 Remarks: Cold, cloudy day. Canopy is still wet after first rain. 75 TABLE A-3 Storm #3 (net throughfall in inches) October 19,R
1970 1.00"
Depth:R
Intensity:R
0.25"/hr. Inches
Inches
@R
2'
@R
4'
Inches @R
6' Plot #1 Tree #1
0.60
0.70 2
0.70 0.75 3
0.65
0.70 4 0.74
0.75 5
0.60
0.65 6 0.70
0.75 X = 0.67
X =R
0.71 Plot #2 Tree #1
0.7
2
0.7
0.7 0.8 3 0.8
0.8
0.9 4 0.8
0.9 5
0.7
0.8 6 0.7
0.8 = 0.73
0.8 T( = 0.75
I= 0.83 Plot #3 Tree #1
0.8 0.9 2
0.85 0.85 0.9 3 0.70
0.70
0.8 4 0.70
0.8 5
0.70
0.8 6 0.70
0.8 = 0.74
;C =R
0.75 =
0.83 76 TABLE A-3 (Continued) Inches
@R
2'
Inches
@R
4'
Inches @R
6' Plot #4 0.65 0.75 2
0.70 0.80 3
0.65
0.70 4 0.60
0.70 5
0.70
0.75
6
0.70
0.80 Tree #1 0.67
=R
a- = 0.75 Plot #5 Tree #1
0.6
0.7 2
0.7 0.8 3
0.7
0.8 4 0.7
0.8 5
0.7
0.8 6
0.7
0.8 X = 0.68R
Remarks: Cloudy day, canopy wet. X = 0.78 77 TABLE A-4 Storm #4 (net throughfall in inches) October 21,R
1970 0.380" Depth:R
.094"/hr. Intensity:R
Inches
InchesR
Inches @R
@R
4'R
@R
6' 2'
Plot #1 0.20 0.25 2
0.20
0.25 3
0.20
0.23 4
0.20
0.25 5
0.15
0.20 6
0.10
0.20 Tree #1
0.17
X
=
0.24 Plot #2
Tree #1
0.20
2
0.29
0.30
0.30
3
0.25
0.25
0.30
4
0.30
0.35
5
0.15
0.25
6
0.26
0.30
X = 0.24
0.30
= 0.27
0.30
31- =R
Plot #3 Tree #1
0.22 0.30 2
0.29
0.29 0.30 3 0.30
0.31 0.33 4 0.30
0.34 5
0.20
0.25 6 0.30
0.35 X = 0.27
= 0.30
31 =R
0.31
78 TABLE A-4 (Continued)
InchesR
Inches
@R
2'R
@R
4'
Inches
6'
@R
Plot #4
Tree #1
0.20
0.24
2
0.21
0.25
3
0.20
0.25
4
0.19
0.25
5
0.21
0.25
6
0.20
0.22
X = 0.20
X = 0.24
Tree #1
0.23
0.25
2
0.24
0.26
3
0.20
0.26
4
0.16
0.21
5
0.21
0.25
6
0.23
0.26
X = 0.21
X = 0.25
Plot #5
Remarks: Cloudy, very windy.
79 TABLE A-5 Storm #5 (net throughfall in inches)
October 23,R
1970
Depth:R
0.975"
Intensity:R
0.195"/hr.
Inches
Inches
@R
@R
2'
4'
Inches
@R
6'
Plot #1
Tree #1
0.45
0.65
2
0.65
0.62
3
0.62
0.65
4
0.66
0.70
5
0.60
0.69
6
0.50
0.64
X = 0.58
X = 0.66
Tree #1
0.72
0.89
2
0.70
0.76
0.80
3
0.70
0.70
0.78
4
0.90
0.90
5
0.75
0.79
6
0.75
0.80
Plot #2
=R
0.75
0.73
=R
0.83
Plot #3
Tree #1
0.80
2
0.74
0.80
0.80
3
0.72
0.78
0.80
4
0.87
0.90
5
0.85
0.87
6
0.85
0.88
X = 0.80
0.85
= 0.80
= 0.85
80 TABLE A-5 (Continued)
InchesR
Inches
@R
2'R
@R
4'
Inches
@R
6'
Plot #4
Tree #1
0.55
0.67
2
0.60
0.74
3
0.65
0.75
4
0.67
0.79
5
0.60
0.71
6
0.70
0.80
X = 0.63
X = 0.74
Tree #1
0.61
0.72
2
0.63
0.70
3
0.66
0.75
4
0.66
0.76
5
0.70
0.77
6
0.71
0.80
X = 0.66
X = 0.75
Plot #5
Remarks: Cold, cloudy, no stemflow, area very wet.
81 TABLE A-6
Storm #6 (net throughfall in inches)
October 25, 1970
Depth: 0.075"
Intensity: 0.075"/hr.
Inches
Inches
@R
@R
4'
2'
Inches
@R
6'
Plot #1
Tree #1
trace
trace
2
trace
trace
3
0.01
0.02
4
0.02
0.03
5
0.02
0.03
6
trace
trace
5
=R
.008
=
0.01
Plot #2
Tree #1
0.05
0.06
2
trace
0.01
0.03
3
0.03
0.05
0.05
4
0.06
0.06
5
trace
0.01
6
0.03
0.04
TC = 0.03
= 0.03
= 0.04
Plot #3
Tree #1
0.04
2
0.02
0.03
0.04
3
0.05
0.06
0.06
4
0.04
0.05
5
0.02
0.04
6
0.06
0.06
= 0.04
0.05
= 0.04
= 0.05
82
TABLE A-6 (Continued)
Inches
2'
@R
Inches
@R
4'
Inches
6R
'
Plot #4
0.01
0.02
2
trace
0.01
3
trace
0.01
4
0.03
0.04
5
0.02
0.03
6
0.02
0.03
X = 0.01
X = 0.02
Tree #1
0.02
0.03
2
0.01
0.02
3
0.02
0.03
4
0.02
0.03
5
0.02
0.02
6
0.01
0.01
Tree #1
Plot #5
X = 0.01
Remarks: Cloudy, canopy very wet.
0.02
=R
83 TABLE A-7
Storm #7 (net throughfall in inches)
October 25, 1970
Depth: 1.20"
Intensity: 0.22"/hr.
Inches
Inches
@R
2'
@R
4'
Inches
@R
6'
Plot #1
Tree #1
0.80
0.90
2
0.90
0.95
3
0.85
0.90
4
0.90
0.95
5
0.80
0.90
6
0.90
0.95
X = 0.86
X = 0.92
Tree #1
0.90
0.95
2
0.90
0.90
0.95
3
0.95
0.95
1.00
4
0.90
0.95
5
0.80
0.90
6
0.85
0.90
Plot #2
= 0.90
0.92
=R
= 0.94
Plot #3
Tree #1
0.90
2
0.95
0.95
1.00
3
0.80
0.85
0.90
4
0.90
0.95
5
0.90
1.00
6
0.90
0.95
= 0.90
0.95
= 0.90
= 0.96
84 TABLE A-7 (Continued) Inches
@R
2'
Inches
@R
4'
Inches
@R
6'
Plot #4
Tree #1
0.80
0.90
2
0.80
0.90
3
0.85
0.95
4
0.90
0.95
5
0.90
0.95
6
0.90
1.00
X = 0.86
7= 0.93
Plot #5 Tree #1
0.70
0.85 2
0.85 0.95 3
0.85 0.95 4
0.85 0.95 5
0.90 0.90 6 0.90
0.90
I= 0.87R
X
= 0.92
Remarks: Canopy was still wet from rain #6 about 7 hours before. Cloudy day. 85 TABLE A-8
Storm #8 (net throughfall in inches)
October 26, 1970
Depth: 0.11"
Intensity: 0.22"/hr.
Inches
Inches
@R
2'
@R
4'
Inches
@R
6'
Plot #1
Tree #1
0.07
0.08
2
0.08
0.08
3
0.07
0.08
4
0.07
0.08
5
0.08
0.09
6
0.08
0.09
X = 0.07
X = 0.08
Tree #1
0.09
0.09
2
0.08
0.08
0.08
3
0.07
0.08
0.08
4
0.09
0.09
5
0.09
0.09
6
0.08
0.09
Plot #2
X = 0.08
i = 0.08
1 = . 085
Plot #3
0.09
Tree #1
0.09
2
0.08
0.08
0.09
3
0.08
0.09
0.09
4
0.08
0.09
5
0.08
0.09
6
0.08
0.09
IC = 0.08
5.-c =R
0.08
0.09 '5: =R
86 TABLE A-8 (Continued) Inches
2'
@R
Inches
@R
4'
Inches @R
6' Plot #4
Tree #1
0.08
0.09 2
0.07
0.08 3
0.08
0.08 4
0.08
0.08 5
0.07
0.08 6
0.07
0.08 X = 0.075
X = 0.08 0.08 0.09 2
0.08 0.09 3
0.09 0.095 4 0.07 0.08 5
0.08 0.08 6
0.08 0.09 = 0.08 = 0.09 Plot #5 Tree #1
Remarks: Clear, sunny, canopy drying quickly. 87 TABLE A-9
Storm #9 (net throughfall in inches)
October 30, 1970
Depth: 0.10"
Intensity: 0.10"/hr.
Inches
Inches
@R
@R
4'
2'
Inches
@R
6'
Plot #1
Tree #1
0.06
0.07
2
0.07
0.08
3
0.07
0.07
4
0.08
0.08
5
0.07
0.07
6
0.07
0.07
5: = 0.07
X = 0.07
Tree #1
0.09
0.09
2
0.08
0.085
0.09
3
0.08
0.085
0.09
4
0.08
0.09
5
0.07
0.08
6
0.08
0.08
Plot #2
X = 0.08
= 0.085
= 0.09
Plot #3
Tree #1
0.09
2
0.09
0.09
0.09
3
0.06
0.07
0.07
4
0.09
0.09
5
0.09
0.09
6
0.08
0.0S
X = 0.08
0.09
= 0.08
= 0.09
R
88
TABLE A-9 (Continued)
InchesR
InchesR
Inches
@ 2'R
@ 4'R
@ 6'
Plot #4
Tree #1R
0.07R
0.08
2R
0.06R
0.07
3R
0.07R
0.07
0.07R
4R
0.07
5R
0.07R
0.06
6R
0.07R
0.08
= 0.07R
I= 0.07
Plot #5
Tree #1R
0.07R
0.08
2R
0.08R
0.08
3R
0.07R
0.08
0.08R
4R
0.08
0.06R
5R
0.07
0.07R
6R
0.08
X = 0.07R
X = 0.08
Remarks: Cloudy, cold, tree trunks are very dry. No stemflow.
87 TABLE A-10
Storm #10 (net throughfall in inches)
October 30,R
1970
Depth:R
0.30"
0.50"/hr.
Intensity:R
Inches
Inches
@R
2'
@R
4'
Inches
@R
6'
Plot #1
Tree #1
0.13
0.15
2
0.12
0.16
3
0.13
0,15
4
0.13
0.16
5
0.14
0.17
6
0.13
0.16
X = 0.13
X = 0.16
Tree #1
0.16
0.19
2
0.17
0.18
0.20
3
0.19
0.20
0.22
4
0.19
0.22
5
0.20
0.23
6
0.20
0.24
Plot #2
X = 0.18
= 0.19
= 0.22
Plot #3
Tree #1
0.19
2
0.18
0.20
0.24
3
0.20
0.22
0.25
4
0.19
0.24
5
0.19
0.24
6
0.20
0.26
X = 0.19
0.25
=R
0.21
= 0.24
90 TABLE A-10 (Continued) Inches
@R
2'
Inches
@R
4'
Inches @R
6' Plot #4
Tree #1
0.13
0.16
2
0.14
0.17
3
0.14
0.17
4
0.15
0.18
5
0.14
0.17
6
0.14
0.17
= 0.14
X = 0.17
Plot #5
Tree #1
0.15
0.17
2
0.15
0.17
3
0.16
0.19
4
0.16
0.18
5
0.14
0.18
6
0.14
0.17
5:
Remarks:
0.15
=R
Cloudy, cold.
Very windy.
Canopy very wet.
X = 0.17
Stems dry - no stemflow.
91 TABLE A-11 Storm #11 (net throughfall in inches) November 2,R
1970 Depth:R
0.9680" Intensity:R
.240"/hr. Inches
Inches
@R
2'
4'
@R
Inches 6' Plot #1
Tree #1
0.43
0.60 2
0.63
0.65 3
0.65
0.70 4
0.65
0.70 5
0.60
0.65 6
0.48
0.50 X = 0.57
X = 0.63 Plot #2 Tree #1
0.70 2
0.72 0.74 0.82 3
0.72 0.75 0.83 4 0.70 0.79 5
0.71
0.81 6 0.70 0.80 TC = 0.71
0.80 = 0.74 = 0.80 Plot #3 Tree #1
0.75 0.80 2
0.80
0.80 0.85 3
0.80
0.80 0.85 4 0.79 0.83 5
0.79 0.83 6 0.80
0.85 X = 0.79
X= 0.80
X = 0.83 92 TABLE A-11 (Continued)
Inches
@R
2'
Inches
@R
4'
Inches
@R
6'
Plot #4
Tree #1
0.55
0.63
2
0.60
0.70
3
0.64
0.74
4
0.61
0.74
5
0.60
0.71
6
0.60
0.70
X = 0.60
X = 0.70
Tree #1
0.61
0.71
2
0.63
0.73
3
0.63
0.71
4
0.60
0.70
5
0.60
0.70
6
0.60
0.70
X = 0.60
X = 0.71
Plot #5
Remarks:
Cloudy, area very wet.
slightly windy.
Stems very dry, no stemflow,
93 TABLE A-12
Storm #12 (net throughfall in inches)
November 3,R
1970
Depth:R
0.18"
Intensity:R
0.09"/hr.
Inches
Inches
@R
2'
@R
4'
Inches
@R
6'
Plot #1
Tree #1
0.09
0.11
2
0.11
0.13
3
0.12
0.14
4
0.11
0.13
5
0.11
0.13
6
0.11
0.13
X = 0.11
X = 0.13
Tree #1
0.13
0.15
2
0.14
0.15
0.16
3
0.13
0.14
0.14
4
0.14
0.15
5
0.14
0.15
6
0.14
0.15
Plot #2
X = 0.14
= 0.14
= 0.15
Plot #3
Tree #1
0.14
2
0.15
0.15
0.16
3
0.13
0.14
0.15
4
0.14
0.15
5
0.14
0.15
6
0.15
0.15
7
= 0.14
0.16
= 0.14
= 0.15
94 TABLE A-12 (Continued) Inches
@R
2'
Inches
@R
4'
Inches
@R
6'
Plot #4
Tree #1
0.09
0.11
2
0.12
0.14
3
0.11
0.13
4
0.12
0.14
5
0.11
0.13
6
0.12
0.13
0.11
=�
X = 0.13
Plot #5 Tree #1
0.10
0.11 2
0.12 0.13 3
0.11 0.12 4
0.13 0.14 5
0.13 0.14 6 0.13
0.13 X = 0.12
X = 0.13 Remarks: Sunny, slightly windy. No stemflow - area drying out. 95 TABLE A-13
Storm #13 (net throughfall in inches)
November 5, 1970
Depth:R
1.05"
Intensity:R
0.35"/hr.
Inches
Inches
@R
2'
@R
4'
Inches
@R
6'
Plot #1
Tree #1
0.61
0.70
2
0.70
0.72
3
0.67
0.75
4
0.68
0.75
5
0.70
0.77
6
0.70
0.76
X = 0.68
X = 0.74
Tree #1
0.74
0.80
2
0.75
0.78
0.84
3
0.76
0.79
0.85
4
0.75
0.85
5
0.77
0.89
6
0.74
0.83
Plot #2
= 0.75
Plot
= 0.78
X = 0.84
#3
Tree #1
0.70
2
0.80
0.80
0.85
3
0.70
0.75
0.80
4
0.70
0.80
5
0.75
0.85
6
0.75
0.85
X = 0.75
0.80
X = 0.80
X = 0.83 96 TABLE A-13 (Continued) InchesR
Inches
@R
2'R
@R
4'
Inches
@R
6'
Plot #4
Tree #1
0.67
0.73
2
0.70
0.76
3
0.70
0.75
4
0.70
0.75
5
0.68
0.73
6
0.66
0.72
X = 0.69
X = 0.74
Plot #5 Tree #1
0.70
0.80 2
0.70
0.80 3
0.72
0.81 4
0.70
0.79 5
0.68
0.77 6
0.70
0.80 = 0.70
X = 0.79 Remarks: Very cloudy, cold, slight breeze, low clouds, Stems are dry - no stemflow. 97
TABLE A-14
Storm #14 (net throughfall in inches)
November 6,R
1970
Depth:R
0.05"
Intensity:R
0.05"/hr.
Inches
Inches
2'
@R
4'
@R
Inches
@R
6'
Plot #1
Tree #1
trace
trace
2
trace
trace
3
0.01
0.02
4
0.01
0.01
5
0.01
0.02
6
trace
trace
=R
.005
X =R
.008
Plot #2
Tree #1
0.02
0.03
2
trace
0.01
0.01
3
0.02
0.03
0.03
4
0.03
0.03
5
0.01
0.01
6
0.01
0.01
= 0.01
=R
0.02
= 0.02
Plot #3
Tree #1
0.01
2
0.02
0.03
0.03
3
0.02
0.03
0.03
4
0.02
0.03
5
0.03
0.04
6
0.02
0.03
X = 0.02
0.02
= 0.03
= 0.03 R
98 TABLE A-14 (Continued) InchesR
Inches InchesR
@
4'R
@ 6' @ 2'R
Plot #4
0.1R
Tree #1R
0.2
traceR
2R
trace
traceR
3R
trace
0.01R
4R
0.02
0.01R
5R
0.01
0.01R
6R
0.02
Y= .006R
X = 0.01
Plot #5 0.01R
Tree #1R
0.01 traceR
2R
0.01 0.01R
3R
0.02 0.01R
4R
0.01 0.01R
5R
0.01 traceR
6R
trace X = .006R
X = 0.01
Remarks: Cold, low clouds, canopy very wet. Stems dry, no stemflow. No breeze. 99
TABLE A-15
Storm #15 (net throughfall in inches)
November 11,R
1970
Depth:R
0.460"
Intensity:R
0.153"/hr.
Inches
Inches
@R
@R
2'
4'
Inches
@R
6'
Plot #1
Tree #1
0.20
0.24
2
0.23
0.26
3
0.21
0.25
4
0.20
0.25
5
0.20
0.27
6
0.20
0.26
X = 0.20
X = 0.25
Tree #1
0.34
0.40
2
0.35
0.37
0.41
3
0.33
0.36
0.40
4
0.36
0.42
5
0.34
0.39
6
0.34
0.40
Plot #2
=
0.34
= 0.36
= 0.40
Plot #3
Tree #1
0.35
2
0.36
0.38
0.43
3
0.36
0.38
0.43
4
0.39
0.45
5
0.37
0.41
6
0.37
0.41
= 0.37
0.42
X = 0.38
-
X = 0.42
100 TABLE A-15 (Continued) Inches
2' @R
InchesR
Inches @R
4'R
@R
6' Plot #4 0.20 0.25
2
0.21
0.26
3
0.22
0.26
4
0.24
0.30
5
0.20
0.25
6
0.20
0.25
X = 0.21
X = 0.27
Tree #1 Plot #5 0.23
0.27 2
0.24 0.29 3
0.25 0.30 4
0.25 0.31 5
0.25 0.30
6 0.25
0.30 Tree #1
X = 0.25R
X = 0.29 Remarks: Cold, cloudy, foggy, canopy very wet, stems are dry.